Well I'm trying to think of how I can explain that dragging a pointy thing over less material will cause less drag without making either of us sound dumb?
New Linn Tonearm - 'Arko' and MC cartridges
- Thread starter paulski
- Start date
Well I'm trying to think of how I can explain that dragging a pointy thing over less material will cause less drag without making either of us sound dumb?
Craig B
Re:trophile
As is your commitment to blind adulation of a single brand.
Author: Alexandrovich, George
Affiliation: Fairchild Recording Equipment Corp., Long Island City, NY
JAES Volume 9 Issue 2 pp. 166,168; April 1961
Publication Date: April 1, 1961
Permalink: http://www.aes.org/e-lib/browse.cfm?elib=469
If you look at the first page of Alexandrovich's 'Letters to the Editor' pages you'll get the impression that you are correct in your assumptions; that is, until you see the graph of 'measured' modulated groove friction coefficients, as they relate to groove position across the record, for the same materials, on page 2.
Unfortunately, access to the full document requires AES membership. On the other hand, should you Google 'Alexandrovich, A Stereo Groove Problem' you will find plagiarized copies about (I'll not link to them here).
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david ellwood
Kirabosi Kognoscente
I have no idea if the new arm is any good, I’m not particularly impressed with the cosmetics in the photos but I’ve not seen or heard one in the wild so will reserve judgement.
As far as blind adulation goes, the list of Linn products I like is shorter than the list of products I don’t but I’m careful to give opinions based on actual experience rather than just bias.
MC cartridges are loaded (according to taste and preferred SQ) by the phono stage. This loading must constrain the degree of movement of the cantilever within the magnets (and thus modify the voltage generated by that movement and thus the frequency response of the cartridge ) by making it more or less hard to move left and right and up and down. (A poor analogy would be trying to drive a speaker in a pressurised sealed container - the more pressure the harder the amplifier would have to work to achieve the same cone movement).
So a heavily loaded cartridge would find it harder to respond to the hills and valleys of the record groove in comparison with a light one. So the "drag on the pointy thing" is not just a function of rotational speed or mass loading.
But are we not talking about friction here rather than drag? Drag is a fluid dynamics concept and is a force which does vary with velocity (boat hulls, F1 aerodynamics, etc.) but kinetic friction is a force which is, I think, independent of speed but does depend on mass (the mass loading of the cartridge) and the coefficient of friction (a function of how wobbly the groove is and the surface materials of the groove and stylus, and the cartridge electrical loading). The ability of the stylus to track the wobbles would therefore affect the coefficient of friction, because of the greater or lesser force required to move the stylus left and right and up and down to navigate the surface variations - a heavily electrically loaded stylus would tend to move the tonearm itself rather than the cantilever with respect to the tonearm and thus more force is required.
Way out of my depth here so happy to be corrected.
So a heavily loaded cartridge would find it harder to respond to the hills and valleys of the record groove in comparison with a light one. So the "drag on the pointy thing" is not just a function of rotational speed or mass loading.
But are we not talking about friction here rather than drag? Drag is a fluid dynamics concept and is a force which does vary with velocity (boat hulls, F1 aerodynamics, etc.) but kinetic friction is a force which is, I think, independent of speed but does depend on mass (the mass loading of the cartridge) and the coefficient of friction (a function of how wobbly the groove is and the surface materials of the groove and stylus, and the cartridge electrical loading). The ability of the stylus to track the wobbles would therefore affect the coefficient of friction, because of the greater or lesser force required to move the stylus left and right and up and down to navigate the surface variations - a heavily electrically loaded stylus would tend to move the tonearm itself rather than the cantilever with respect to the tonearm and thus more force is required.
Way out of my depth here so happy to be corrected.
Craig B
Re:trophile
The gist of my comment was based upon observation of the photos released by Linn themselves combined with actual experience of tonearms that lack decoupled counterweights. You offered that there could well be rubber rings within the weight, to which I expressed disappointment should these be also used as 'nuts' to facilitate adjustment along a threaded end stub. Of course, this would work, however, I can't see it offering long term consistency and/or reliability. If any personal bias has been expressed, it was aimed at possible design choices at this point (well, that and a wee piss take at certain Linn dealers). No doubt, I'll be pulling the counterweight off the first one that shows up here.
david ellwood
Kirabosi Kognoscente
I have offered no opinions on this arm, I haven’t heard or seen one , it’s a completely unknown quantity.
Craig B
Re:trophile
My sincerest apologies, it was Paul R who offered that assumption.
robbyd
pfm Member
At a speed of zero rpm there will be no friction or drag.
This proves that friction is speed related.
Paul R
pfm Member
I'd forgotten about the top price cart and phono stage. They make the Planar 10 itself look ridiculously good value.,,,
I was tinkering with the oldish P3 I bought last summer for my daughter to use, fitted with the RB300 I bought way back in 1984 and a AT VM95E. I think I'd want a better stylus, but if I had to it wouldn't be a problem.
tpetsch
...The rhythm has Control
At a speed of zero rpm there will be no friction or drag.
This proves that friction is speed related.
That's true for Kinetic Friction, but not for Static Friction. ...Although there are some forms of Kinetic Friction that can actually speed things up "In common language acceleration means an object speeds up, but in physics acceleration is any change (faster or slower) in velocity over time." In fact depending on the music recorded in the grove -loud vs. quiet sections- the stylus is tracking at the moment the platter may be actually slowing down or speeding up -aka
accelerating- continually applying forces thru all X, Y & Z axis upon the stylus tip, cantilever, body, tube and bearings of the Tone Arm, LP playback it's not as simple as just a consistent one dimensional "pull" on the stylus.. There are stylus drag Youtube Videos that demonstrate this phenomenon in real time FWIW.
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sonddek
Trade: SUPATRAC
I don't mind sounding dumb. Done it all my life. Explain away. I think you have made an intuitive but possibly false assumption that drag from slippage is largely proportional to speed. As I've said, I don't think the relationship between drag and speed is all that strong especially on some plastic surfaces. In fact, sometimes drag seems to get less when you go faster, a bit like ski-ing in deep snow...
Paul R
pfm Member
Yet it seems standard practice to use O rings on a smooth stub to hold a counter-weight in place then apply downforce with a spring. My 84 RB300 and 88 Ekos both do this, and both still work just fine.
So I remain open minded. And I recall an LVX where the counterweight was threaded in some way to apply downforce with some appearance of precision. Otherwise quite unpleasant arm physically.
Paul R
pfm Member
I'm an unreliable source. But I've been playing with a DC motor drive. The average current to turn the platter at 33ish rpm with no other load might be 34.8mA, playing the first track that rises to 37mA and an inner track it only reaches 36mA. I've not sanity checked or repeated these measurements much yet, and there's a covariance of the rpms slowing to account for. But
Anyway you can turn current and voltage (about 1.38v in this particular case) into power, and power into drag given velocity. The required anti-skate clearly reduces as the stylus makes its way towards the centre.
I've not searched patents but it seems obvious (and therefore in the bizarre world of intellectual property, patentable) that a motor controller such as a Radikal could deduce the stylus drag moment by moment by evaluating the motor's power requirement and consequently drive an electromagnetic antiskate application device.
sonddek
Trade: SUPATRAC
After following your advice to do a search I see that I've dragged you around this track before and I have no memory of it. I'm only 54
Apologies.That said, the research you link does seem to back up my intuition that radius makes almost no difference to drag, even on modulated grooves, unless you're tracking at 4 or 5 grams. These graphs are distinctly flat when compared to the graphs in the AES research into the effect of signal strength on drag, which generally show a very strong influence.
In other words, my assumption that signal sends required bias all over the place and dwarfs, if not rendering negligible, any dependency on radius, isn't far wrong.
Looks like SME were right. Dangling a weight on a string is very close to as good as is practically possible and a mechanism providing increasing bias as the stylus progresses is probably farting against thunder.
Tim Jones
pfm Member
My suspicion is that the P10 just is ridiculously good value for money.
The relationship between friction and speed is very strong, be it the clutch on a car or the space shuttle entering the atmosphere. The latter famously needed tiles adding to the outside to protect it from friction heat from the air molecules.
